Exploring Neutrinos from Kaon Decay in MiniBooNE Experiment

1. Neutrinos from kaon decay in MiniBooNEKendall MahnColumbia University • MiniBooNE beamline overview • Kaon flux predictions • Kaon measurements in MiniBooNE • high energy events • Summary

2. MiniBooNE beamline • MiniBooNE is searching for nm to ne oscillations • Produce a beam of nm, look for ne • 8 GeV protons hit Be target, producing: • p+ (primary source of nm ) • K+/- (decay to nm, ne) • K0 (decay to ne )

3. Oscillation search backgrounds ne p0 • Three major backgrounds: • misID’d p0s • constrained by observed p0s • nefrom muon decay • muon produced for each nm, constrained via nm spectrum • nefrom kaon decay nm m+ e+ p+ ne nm ne K+, K0

4. K+ flux predictions • All flux predictions are from a parameterized fit to external data with uncorrelated uncertainties • K+ external data shown here in transverse momentum (pT ) vs x F • Feynman x, the longitudinal momentum / maximum allowed longitudinal momentum • Currently use Aleshin, Abbot, Eichten, Piroue and Vorontsov data p T (GeV/C) x F

5. Measurements of kaons in MiniBooNE • MiniBooNE is a blinded analysis: • we can’t look at ne -like events at energies where there might be oscillation events • must measure kaons outside the signal region and extrapolate

6. Measurements of kaons in MiniBooNE • Measure kaons via muons: Little Muon Counter (LMC) • Large angle muons are predominantly from kaon decays (higher allowed pT for muons from kaons) • Count muons at 7o angle from decay pipe and determine corresponding kaon rate • Measure kaons via neutrino events: high energy “box” • A neutrino from a kaon will have a higher energy than if it came from a pion of the same momentum • Highest energy tank events tend to be from K+ • Directly measure ne background in different energy region

7. Neutrino Events in MiniBooNE • 12 m diameter light detector filled with mineral oil • 1280 PMTs in inner region • 240 PMTs in outer “veto” region • Neutrino events emit Cherenkov light in a characteristic pattern for different events • Muons have long tracks, constant light over distance • Electrons have shorter tracks; scattering causes the ring to be “fuzzier” e m

8. Neutrino Interactions • Charged Current Quasi-elastic (CCQE) • Energy of neutrino is related to the outgoing leptons’ energy and angle l+ nl • mpEl - ml2/2 • En(QE)= p • mp - El + √(El2 -ml2) cos qm n • Charged Current Pion production (CCp) l nl C p+ X

9. High Energy Box Event selection: • Event is in time with the beam • Has a En(QE) (assuming muon) > 1.5 GeV, < 4 GeV • Passes cosmic ray reduction cuts • within forward cone along the beam direction • Veto hits less than 30 • Entering cluster hits less than 1 • Less than 1 hit in the veto corresponding to the track direction m x x x m nm

10. High Energy Box Monte Carlo p+ K+ K0, m,p- Predominantly p+ below 2 GeV, predominantly K+ above En (QE) in GeV 1.5 GeV

11. High Energy Box: nm events Preliminary • Look at CCQE, CC p+nm events as a check of p+, K+ • long tracks consistent with muon • veto hits<6 (contained) Total MC Data(stat only) p +K+ Note: All plots are relatively normalized to 1 Absolutely normalized plots show a normalization difference of ~50% => MiniBooNE is working on this 1.5 GeV En(QE) in GeV logarithmic scale

12. High Energy Box: nm events Preliminary • Look at CCQE, CC p+nm events as a check of p+, K+ • long tracks consistent with muon • veto hits<6 (contained) Total MC Data(stat only) CCQE CC p + Note: All plots are relatively normalized to 1 Absolutely normalized plots show a normalization difference of ~50% => MiniBooNE is working on this 1.5 GeV En(QE) in GeV logarithmic scale

13. High Energy Box: ne events • Look at CCQE ne events as a check of all ne backgrounds • run the ne PID prepared for the oscillation analysis on this sample Preliminary Preliminary Oscillation K+ misIDK0 m p+HE box data (stat only) En(QE) (electron) GeV

14. High Energy Box: ne events • Look at CCQE ne events as a check of all ne backgrounds • run the ne PID prepared for the oscillation analysis on this sample Preliminary Oscillation K+ misIDK0 m p+ HE box data (stat only, 3.25e20 pot) En(QE) (electron) GeV

15. Using the HE box • The different event samples in the HE provide checks of the predicted neutrino from kaon rate • Example: CCQE contained events: • 2 subevents, decay michel electron energy <70 MeV, veto hits < 6, muon-like track • ~11K data events for 5e20 pot, 82% CCQE, 15% CCp • 17% error due to cross sections, 5% due to flux, 7% optical model

16. Summary • MiniBooNE is searching for nm to ne oscillations • Observing these oscillations depends on understanding the content of the neutrino beam • The HE box and LMC provide MiniBooNE with checks using the same beamline of the kaons • Check of K+ m from the LMC • Check of p+, K+ nm from HE box CCQE, CCpi muon-like events • Check of K0, K+ ne from HE box CCQE electron-like events